April, I really like the way you are going on this. I did a draw over to show you some of my thoughts. Hope you don't mind.

I like the diagonal you have with her body and arm leading down to the goblet. I think lengthening her tail and curving will help. Also give her hair some more shape. The shoulder anatomy is a bit wonky. I think her fingers should break the curved plane of that foreground glowing coral(?). That coral is a great opportunity for a secondary light source. But I'd go with pink/purple glow as a contrast to the blue background glow.

You colored the goblet how it might appear in a room on land so it looks out of place in this beautiful dark, glowy world you've created. Gold does have a local color, but as a reflective surface it would also reflect it's environment. The closer it is to you the more you would see the gold with highlights from the lights and darks surrounding it.

The blue background light can also be an opportunity for some rim lighting where her head and arms cross in front of it.

Maybe add some more seaweed across the bottom. Again breaking the curved plane of that coral.

It's looking great! Really not at all far off from where I think you want it to be.